Spectrum used in an existing wireless communications system is classified into two types: licensed spectrum (English: licensed spectrum) and unlicensed spectrum (English: unlicensed spectrum). Any operator may deploy a device in an unlicensed frequency band, for example, wireless fidelity (English full name: wireless fidelity, English acronym: WiFi) devices in a 2.4 GHz frequency band and a 5 GHz frequency band.
For a Long Term Evolution (English full name: Long Term Evolution, English acronym: LTE) node deployed in an unlicensed (English: unlicensed) frequency band (LTE-U node for short), that is, an LTE node (for example, a base station) deployed in an unlicensed frequency band, each LTE-U node may suffer interference caused by sending data by another LTE-U node. To reduce interference as much as possible, in the prior art, user equipment first performs joint estimation on an entire channel, and the user equipment sends channel state information (English full name: channel state information, English acronym: CSI) to a base station according to a joint estimation result, and then the base station sends data according to the CSI information.
However, an LTE-U node suffers different interference when sending data in different time periods. Therefore, interference suffered by the LTE-U node when the LTE-U node sends any data cannot be faithfully reflected by CSI information that is of the entire channel and that is sent by the user equipment.